FXUS62 KRAH 060223
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1023 PM EDT SAT JUL 5 2008

.SYNOPSIS...
A STATIONARY FRONT WILL REMAIN STALLED ACROSS VIRGINIA AND WEST
VIRGINIA. A WARM AND HUMID AIRMASS WILL REMAIN IN PLACE SUPPORTING
THE DEVELOPMENT OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS
THROUGH MONDAY.
&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 1020 PM SATURDAY...

SCT CONVECTION PERSISTING ACROSS PORTIONS OF CENTRAL NC LATE THIS
EVENING. CONVECTION FORMED THIS AFTERNOON ALONG A CONVERGENCE
BOUNDARY DRIVEN BY A REGION OF DIFFERENTIAL HEATING IN A
MODERATELY UNSTABLE AIRMASS. THE SFC BOUNDARY GENERALLY EXTENDED
FROM THE NORTHERN COASTAL PLAIN SW ACROSS THE PIEDMONT AND INTO
UPSTATE SC. HIGH TEMPS RANGED FROM 93 AT KFAY AND 92 AT KRWI TO 82
AT KGSO AND 80 AT KINT.

CONVECTION THIS EVENING PRODUCED VERY HEAVY RAIN WITH KRWI
REPORTING MORE THAN 3 INCHES OF RAIN THIS AFTERNOON. COCORAHS
SPOTTERS REPORTED 0.98 INCHES OF RAIN IN 60 MINUTES NEAR
BURLINGTON AND A SKYWARN SPOTTER REPORTED 1.30 INCHES OF RAIN IN
LESS THAN 25 MINS NEAR CHAPEL HILL. 00Z KGSO RAOB WAS VERY MOIST
WITH PW VALUES OF 1.71 OR AROUND 140 PERCENT OF NORMAL SUPPORTIVE
OF FLASH FLOODING.

SCT CONVECTION SHOULD PERSIST THROUGH THE OVERNIGHT HOURS AS
UPPER TROF REMAINS TO OUR WEST WITH SEVERAL PERTURBATIONS IN THE
CYCLONIC FLOW ALOFT APPROACHING THE REGION. WILL GRADUALLY SCALE
BACK POPS FROM LIKELY RANGE AROUND MIDNIGHT TO CHANCE AROUND
DAYBREAK. BOUNDARY LAYER HAS LARGELY STABILIZED AND THE THREAT OF
SVR WEATHER HAS DISSIPATED. BUT HIGH MOISTURE CONTENT OF ATMOS
WILL MAINTAIN THE THREAT OF HEAVY RAIN OVERNIGHT.

LOWS TONIGHT SHOULD RANGE IN THE UPPER 60S TO LOWER 70S WITH
MOSTLY CLOUDY SKIES.

SUNDAY SHOULD BE A SIMILAR PERFORMANCE OF TODAY WITH NUMEROUS SHOWERS
AND THUNDERSTORMS BREAKING OUT IN THE AFTERNOON HOURS. MLCAPES
ONCE AGAIN RISE TO 1500-2000 J/KG AND PRECIPITABLE WATERS REMAIN
AROUND 2 INCHES. UPPER LEVEL DIVERGENCE WILL PERSIST ACROSS THE
REGION WITH THE TROUGH AXIS ORIENTED NORTH TO SOUTH ACROSS THE
OHIO AND TENNESSEE VALLEYS. IF ANY SUBTLE SHORTWAVES ROTATE OUT OF
THE BASE OF THE TROUGH...THEY WILL ONLY SERVE TO FURTHER ENHANCE
CONVECTIVE COVERAGE ACROSS CENTRAL NORTH CAROLINA. POPS ONCE AGAIN
WELL INTO THE LIKELY RANGE. PERSISTENCE FOR HIGHS... GENERALLY MID
TO UPPER 80S.

SEVERE POTENTIAL WILL BE ISOLATED ONCE AGAIN DUE TO WEAK SHEAR. HIGH
PRECIP WATERS POINT TO HEAVY RAINFALL AND LOCALLY DAMAGING WET
MICROBURSTS AS THE MAIN THREATS WITH THE STRONGER STORMS. FLASH
FLOODING MAIN BE THE MORE SIGNIFICANT ISSUE AS HIGH PW VALUES WILL
ONCE AGAIN SUPPORT CONVECTION WITH HEAVY RAIN.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
AS OF 130 PM SATURDAY...

SUNDAY NIGHT:
THE UPPER LOW JUST TO OUR WEST OVER THE TN/OH VALLEYS IS EXPECTED TO
BEGIN TO WEAKEN SUNDAY NIGHT THROUGH MONDAY MORNING AS IT DRAWS
CLOSER TO THE SOUTHERN APPALACHIANS. EVEN SO...THERE ARE STILL
INDICATIONS THAT SOME SHORTWAVE ENERGY ROUNDING THE BASE OF THE
UPPER LOW WILL CROSS FROM SOUTH TO NORTH OR SSW TO NNE OVER CENTRAL
NC AT SOME POINT(S) DURING THE NIGHT. ADDITIONALLY...FCST SOUNDINGS
SHOW ABOVE NORMAL PRECIPITABLE WATER VALUES (AROUND 2.00")
THROUGHOUT THE NIGHT. A VERY MOIST JULY ATMOSPHERE PLUS AN UPPER LOW
JUST TO THE WEST IS MORE THAN ENOUGH REASON TO KEEP IN A CHANCE
(30-40%) OF SHOWERS/STORMS THROUGHOUT THE NIGHT. COVERAGE WILL
DEPEND ON THE EXTENT OF UPPER LEVEL LIFT DURING THE NIGHT AND ALSO
ON ANY PRE-EXISTING CONVECTION AND ASSOC OUTFLOW BOUNDARIES
LINGERING FROM AFTERNOON/EVENING CONVECTION ON SUNDAY. LOW TEMPS
WILL BE MILD...IN THE UPPER 60S TO LOWER 70S.

MONDAY:
THE UPPER LOW IS EXPECTED TO HAVE WEAKENED TO AN OPEN WAVE BY THIS
TIME...AND SHOULD BE LOCATED SOMEWHERE ALONG THE SOUTHERN
APPALACHIANS (WESTERN NC/VA AND WV MOUNTAINS). BOTH THE 12Z NAM/GFS
SHOW THE UPPER WAVE ENTERING THE FOOTHILLS OR FAR WESTERN PIEDMONT
BY 00-06Z TUE MORNING. FCST SOUNDINGS ARE CONTINUING TO SHOW A VERY
MOIST AIRMASS ACROSS THE ENTIRE AREA...WITH PRECIPITABLE WATER
VALUES AROUND 1.75-2.00"...WITH THE LOWER VALUES IN THE WESTERN
PIEDMONT. GIVEN THE PROXIMITY OF THE UPPER LEVEL WAVE TO THE WESTERN
PIEDMONT...THE BETTER UPPER LEVEL LIFT DURING THE DAY MONDAY MAY BE
SHIFTED A BIT EAST TOWARD THE TRIANGLE/FAY AREA AND COASTAL PLAIN.
FOR THIS REASON (IN ADDITION TO BETTER MOISTURE/INSTABILITY IN THE
EAST)...WILL SHOW THE HIGHEST CHANCES FOR SHOWERS/STORMS IN THE
EASTERN HALF OF THE AREA...WITH RELATIVELY LOWER CHANCES IN THE
WESTERN PORTION. HAVE DECIDED TO GO WITH LIKELY POPS (60%) IN THE
COASTAL PLAIN...TAPERING BACK TO LOW/MID CHANCE (30-40%) IN THE FAR
WESTERN PIEDMONT. LOW/MID LEVEL FLOW (0-3 KM) IS 20 KNOTS OR LESS
MONDAY AFTERNOON...GENERALLY NOT ENOUGH TO ORGANIZE CONVECTION...AND
THEREFORE ANY SEVERE THREAT SHOULD BE CONFINED TO ISOLATED CELLS
WITH A PRIMARY THREAT OF STRONG GUSTY WINDS IN DOWNBURSTS DUE TO
WATER LOADING AND EVAPORATIVE COOLING.

MONDAY NIGHT:
THE UPPER LEVEL WAVE IS EXPECTED TO FURTHER DEAMPLIFY OVER THE
MID-ATLANTIC MONDAY NIGHT AS IT PROGRESSES A BIT FURTHER EAST INTO
CENTRAL NC/VA. TOUGH TO SAY WHETHER OR NOT THERE WILL BE CONVECTION
AFTER MIDNIGHT TOWARD SUNRISE TUE...AND THIS WILL LIKELY DEPEND ON
THE LOCATION/COVERAGE OF CONVECTION AND ANY BOUNDARIES AFTER SUNSET
MON EVENING...AND THE EXACT POSITION OF THE UPPER LEVEL WAVE DURING
THIS TIME. WILL NEED TO CARRY AT LEAST A SLIGHT CHANCE OF SHOWERS
AND THUNDERSTORMS ACROSS THE ENTIRE AREA...AND MAY GO WITH LOW
CHANCE (30%) IN THE EASTERN HALF OF THE AREA WHICH IS MORE LIKELY TO
BE IN A BETTER POSITION W/RESPECT TO THE UPPER LEVEL WAVE. WILL GO
WITH PERSISTENCE FOR LOW TEMPS...RANGING FROM THE UPPER 60S TO LOWER
70S. -VINCENT

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 230 PM SATURDAY...

THE UPPER LEVEL PATTERN BECOMES MORE UNIDIRECTIONAL FOR THE REST OF
THE UPCOMING WORK WEEK...WITH VERY BROAD TROUGHING ACROSS THE
EASTERN CONUS...PRIMARILY FROM THE MID-ATLANTIC / TN VALLEY AND
POINTS NORTH. BOTH THE GFS/NAM FORECAST WEAK LEE SURFACE TROUGHING
EACH DAY ACROSS CENTRAL NC...AND FCST SOUNDINGS SHOW A TYPICAL
EARLY/MID JULY ATMOSPHERE WITH ENOUGH MOISTURE/INSTABILITY THAT A
LOW CHANCE (30%) OF SHOWERS/STORMS EACH DAY DURING THE PEAK-HEATING
AFTERNOON/EVENING HOURS LOOKS PRETTY REASONABLE. BETTER CHANCES MAY
BE POSSIBLE FROM WED EVENING THROUGH FRI MORNING WHEN A WEAK FRONT
(ASSOCIATED WITH AN UPPER LEVEL LOW AROUND THE NORTHERN GREAT LAKES
REGION AND A SFC LOW MOVING INTO NEW ENGLAND) MAKES ITS WAY INTO THE
LOWER MID-ATLANTIC AND CAROLINAS. WILL ADVERTISE 40% POPS DURING
THAT GENERAL TIME FRAME. OTHERWISE...HIGH/LOW TEMPS SHOULD BE
NEAR-NORMAL FOR THIS TIME OF YEAR. -VINCENT

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
AS OF 1020 PM SATURDAY...

SCT CONVECTION PERSISTS ACROSS CENTRAL NC WITH FORECAST CONDITIONS
VARYING AT EACH TERMINAL SITE. SCT CONVECTION WILL LIKELY CONTINUE
THROUGH THE OVERNIGHT BEFORE TAPERING OF TOWARD DAYBREAK.

SVR THREAT OF HIGH WINDS AND HAIL HS LARGELY ABATED BUT HIGHER
MOISTURE CONTENT OF ATMOS SUPPORTS HEAVY RAIN POTENTIAL. ALL TAF
SITES HAD PRECIPITATION TODAY WITH MOST SIGNIFICANT PRECIP AT KRWI
AND KRDU WHERE MVFR FOG AND STRATUS IS LIKELY OVERNIGHT.

NUMEROUS SHOWERS AND THUNDERSTORMS ARE ONCE AGAIN EXPECTED SUNDAY
AFTERNOON/EVENING. CBS INCLUDED IN TERMINAL FORECAST FOR SUNDAY
BEGINNING IN THE EARLY AFTERNOON.

UNSETTLED WEATHER WITH MAINLY AFTERNOON AND EVENING CONVECTION
EXPECTED THROUGH THE UPCOMING WORK WEEK WITH POTENTIAL FOR EARLY
MORNING FOG AS WELL.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...BLAES